Design And Implementation Of Underwater Communication System Based On Steel Cable Electromagnetic Channel

The ocean is an important strategic area of the country,a treasure trove of resource reserves,and plays an irreplaceable and important role in ensuring national security,relieving pressure on resources,and regulating global climate.To obtain marine information quickly and reliably,advanced marine communication detection technology is indispensable.Induction-coupled data transmission technology is a technology that uses the principle of electromagnetic induction to achieve underwater contactless signal transmission,which can continuously observe and acquire ocean data for a long time.It is a new method widely used internationally,and has important scientific research significance and practical economic value for the development of China’s marine science and technology.Compared with the traditional underwater wired communication system directly connected by cable and fiber optic cable and underwater wireless communication system based on sound and light,the underwater communication system based on inductive coupling principle of steel cable electromagnetic channel is more economical,reliable and suitable for underwater data transmission,and the location of underwater sensors can be freely selected without restriction,which is convenient for building underwater observation system.The subject has a broad market prospect and can be widely used in buoys,submerged buoys,research vessels,drilling platforms and other marine observation platforms.In this article,the design and implementation of an underwater communication system for electromagnetic channels over steel cables is investigated.The system is based on the principle of electromagnetic induction coupling transmission,using a single-core steel cable can be used for real-time data transmission.The system can mount several underwater sensors at the same time for efficient data transmission.The article firstly investigates the principle and transmission channel of steel cable electromagnetic channel underwater communication.This article establishes a three-level transmission channel model based on COMSOL Multiphysics multi-physics simulation software for transmitting magnetic ring-steel cable,steel cable-seawater,and steel cablereceiving magnetic ring,and specifically analyzes the effects of magnetic ring parameters,seawater,and the number of underwater sensor nodes on the signal transmission channel.According to the established channel model,the amplitude-frequency characteristic curves of the electromagnetic induction coupled transmission channel are obtained by simulating different frequency signals,and on this basis,the carrier frequency of the communication system is optimally selected.Second,for the problem of low carrier frequency and narrow system bandwidth,the thesis investigates the system modulation and demodulation optimization problem,establishes the mathematical model of baseband code-element signal optimization,proposes the solution scheme of the optimization model based on Jacobi polynomial,and obtains the optimized baseband code-element signal expression.Through the comparison and analysis of the baseband code element signal,the optimized signal has the characteristics of fast frequency roll-off and small out-of-band radiation,which achieves the purpose of improving the system frequency band utilization.Based on the optimized baseband code-element signal,the article designs a quadrature modulation and demodulation scheme for the communication system.Through simulation,it is verified that the modulated signal has constant envelope characteristics and the simulation results are consistent with the expectation.Finally,the article uses FPGA as the main chip to implement the hardware circuit and software program design of the underwater one-to-many communication system based on the steel cable electromagnetic channel.The underwater communication system was tested by module test and system interconnection,and the system was improved according to the test results.The reliability and stability of the wireless communication of the underwater system is verified by simulating the underwater environment under laboratory conditions.Next,the shortcomings of this system and the future development prospects are briefly discussed.